1. Field of the Invention
The present invention relates to a cassette and a method for daylight-loading a photographic sheet pack in a photographic processor.
2. Description of the Prior Art
It is known to avoid the use of a darkroom for loading light-sensitive films into a film processor such as a cassette-loading apparatus which automatically reloads radiographic film cassettes with a fresh film after an X-ray exposed film has been removed.
These apparatus usually comprise a film supply magazine in the form of a drawer or the like that can be opened and into which a lighttightly wrapped stack of films is put in daylight conditions. Next, the drawer is closed and an appropriate mechanism cuts the wrapper so that it can be peeled from the film stack manually or automatically. One example of suchlike system is disclosed in U.S. Pat. No. 4,909,389 relating to a film-sheet package for use in the magazine of a reloader for radiographic film cassettes. The film wrapper is in the form of a sleeve having a sealed flap for engagement by a winding mechanism. The end opposite to the sealed flap has an open flap folded inwardly to lighttightly close the package. Opening of the package occurs by winding the sealed flap by means of a winding mechanism, the film stack as such being withheld, so that the sleeve is stripped from the stack of film sheets. Another example of suchlike system is disclosed in Research Disclosure 22936 of May 1983, Havant, Hampshire, GB.
While these systems work satisfactorily for radiographic film, they are unsuited for aluminium offset printing plates, that e.g. must be image-wise exposed in a platesetter, because such plates have right, sharp corners as distinct from the rounded corners of X-ray film, and also the size of these plates can amount to 81.times.111 cm, and the weight of a stack of 30 of them can amount up to 50 kg.
An improved method for lighttightly wrapping and daylight-loading plates of the type referred to has been disclosed in EP 0 718 683 A2 assigned to the same assignee as the one of the present application. This method comprises the steps of wrapping a stack of light-sensitive sheets in a wrapper formed by two congruent lighttight wrapping foils and providing such wrapper with a first peripheral lighttight closure spaced from the four edges of said stack of sheets, providing said wrapper with a clamping, second peripheral lighttight closure located between said first one and the perimeter of said sheet stack, opening said first closure in daylight and loading said wrapped stack of sheets while still closed by said second closure in an opened cabinet, lighttightly closing said cabinet, unclamping said second closure and removing the wrapping foil lying on top of said sheets to set them free for further processing.